linux-kernel - Re: DVD-RAM cannot be mounted RW with 2.6.18/2.6.19

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Date:	Sat, 16 Dec 2006 21:34:47 +0100
From:	Laurent Riffard <laurent.riffard@...e.fr>
To:	"A. Kalten" <akalten@...cast.net>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: DVD-RAM cannot be mounted RW with 2.6.18/2.6.19

Le 16.12.2006 20:55, A. Kalten a écrit :
> Hello,
> 
> DVD-RAM disks previously made with a Linux system can
> no longer be mounted in RW mode.  For some reason, as
> indicated by the error message from the mount command,
> the disks are detected as being write-protected (which
> is not the case).  To be able to write to these disks,
> the mount command must be issued again with the "-o remount"
> option.
> 
> The commands given are as follows.  Although the file
> type in this example is ext2, the same behavior is seen
> also with the udf file type.
> 
> # modprobe ide-cd
> # hdparm -d1 -X udma4 -k1 /dev/hde
> 
> # mount -t ext2 -o rw,noatime /dev/hde /cdrom
> mount: block device /dev/hde is write-protected, mounting read-only
> 
> # mount -t ext2 -o remount,rw,noatime /dev/hde /cdrom
> 
> Now the DVD-RAM disk can be written normally, but there should
> be no need for the second mount command.
> 
> The kernel log for this command sequence seems to show nothing abnormal:
> 
> kernel: hde: ATAPI 39X DVD-ROM DVD-R-RAM CD-R/RW drive, 2048kB Cache, UDMA(66)
> kernel: Uniform CD-ROM driver Revision: 3.20
> kernel: hde: CHECK for good STATUS
> kernel: cdrom: hde: mrw address space DMA selected
> kernel: cdrom open: mrw_status 'not mrw'
> 
> Furthermore, if I attempt to check the unmounted DVD-RAM disk with
> e2fsck, the drive is still reported as read-only:
> 
> # e2fsck -p /dev/hde
> e2fsck: Read-only file system while trying to open /dev/hde
> Disk write-protected; use the -n option to do a read-only
> check of the device.
> 
> However, as I indicated above, the disk is not write-protected.
> 
> I am reporting this problem on the lkml because of a hint
> that I discovered at this link:
> 
> http://lists.opensuse.org/packet-writing/2006-10/msg00000.html
> 
> Although this problem does not involve packet-writing, it may
> be related to the cdrom code.

The problem I reported in the above link was related to UDF filesystem.

AFAIR, my DVD-RW have been formatted with "mkduffs --media-type=dvd",
which toggled a read-only flag at the FS level. I reformatted this DVD-RW 
with "mkudffs --media-type=dvdram" and the problem was gone.

I'm afraid this won't help you...
~~
laurent
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